Deformation of tissues is commonly performed during surgery or other medical procedures either to achieve surgical access or to specifically alter the dimensions of one part of the anatomy. Examples of deformations of tissue for surgical access include spreading ribs during a thoracotomy, spreading a bisected sternum during sternotomy, and separating the vertebrae of the spine for surgery on the intervertebral disk. Examples of deformation of tissues to alter the dimensions of the tissue include distraction to adjust the position of vertebrae. Such deformations will collectively be referred to as “retraction” here.
Spreaders, retractors, distractors, and even trocars (collectively called “retractors”) can impose significant forces on surrounding tissues during retraction. The resulting strain on these tissues, and on associated tissues, such as the ligaments attaching ribs to vertebrae for example, can be large, leading to damage of these tissues, including the fracture of ribs and the rupture or irreversible deformation of ligaments and other fibrous tissues.
Retraction occurs in two different phases—deforming the tissue in a first retraction phase and holding the tissue at that deformation in a second retraction phase. Both are usually done with the same instrument. For example, a rib spreader is used both to force the ribs apart during a thoracotomy (first phase of retraction) and to hold the ribs apart during the surgical procedure (second phase of retraction). In the medical literature, both phases are frequently referred to as retraction.
Both phases of retraction traumatize tissue. Trauma from the first phase of retraction can include the rending and tearing of tissues; bones bend and break; muscles stretch beyond normal limits; ligaments and other connective tissues stretch and tear; nerves are stretched. Trauma from the second phase of retraction can include trauma arising from the force of the retraction device holding the tissue open and can include ischemia of the tissue due to elevated tissue pressure, blockage of nerves, and blockage of blood vessels causing ischemia in tissues distant from retraction.
Tissue trauma and ensuing complications resulting from both phases of retraction can be greater than the trauma resulting from the medical procedure that required the retraction. For example, thoracotomies are extremely traumatic, and can result in post-surgical pain and respiratory complications that exceed that of the thoracic procedure, such as a lung segmentectomy.
There is, therefore, need for improved devices, systems, and methods to perform one or both phases of retraction.